A microcasting process is developed for the production of monocrystalline microwires of pure and alloyed aluminium. The process is based on pressure infiltration of single-crystalline salt moulds; it is capable of producing wires with a diameter between 6 and 100 µm and a length in excess of 1000 µm. The wire has a surface roughness around 30 nm and an initial dislocation density that is roughly 1011 m-2 when the wire diameter is 20 µm. We present results from classical tensile testing on these wires, and also on relaxation testing. Tests aim to probe the initiation and cessation of dislocational plasticity in different ways, which is observed to proceed to a significant extent in the form of large sudden strain bursts. The mechanical tests are supplemented with microscopic investigations of the metal substructure evolution that accompanies the deformation of the wires.